Eyeglasses include small hinges between the lens frame and the foldable temple side elements. Such hinges have a pair of intermeshed pivotable lug sets which define a pin-receiving bore with bore ends opening onto opposed lug set faces. An end lug of one set is typically formed with internal threads. A removable hinge pin with a head at one end and external threads at its other end is inserted threaded end first into the hinge bore opposite the threaded lug, and the threaded end of the pin screws into the threaded lug as the head comes into restraining engagement with the uppermost lug set face.
Small screw-type hinge pins of this conventional design often loosen and even inadvertently come out entirely. They are then frequently lost and, because of their minute size, replacement is an extremely difficult procedure.
It is the principal purpose of the present invention to provide an improved hinge pin with three major design features. First, it is to require no retrofit modification of conventional hinge lugs. Second, it is to be readily removable. Third, it is to be easily insertable by means of an attached break-away insertion tool which can be separated after insertion without leaving unwanted and unnecessary stub parts on the pin.
Several prior art designs have been advanced for eyeglass hinge pins which depart from the common threaded design but which have the disadvantage of requiring substantial special modifications to the lugs of the hinge. Representative of such prior art are U.S. Pat. Nos. 3,594,073, 3,449,430 and 3,110,057. Not only do those designs require retrofit modifications but they are not combined with any form of attached manipulable break-away insertion tool.
Perhaps the closest prior art reference to the objects of the invention enumerated above is U.S. Pat. No. 3,826,565. It does not require retrofit modification of the hinge lugs and it does disclose an attached break-away tool to assist in insertion of the hinge pin. In that design a hinge pin is pulled downwardly through the hinge bore by means of a gripable tool body which is first inserted through the hinge bore and which is attached to that end of the pin remote from its head. This tool body includes a single side barb which together with the tool body itself is slightly oversized in relation to the hinge bore and must therefore undergo some resilient compression as it is pulled through the bore. When it emerges from the bore it then projects a slight extent to one side over the lowermost lug set face. The tool body is then cut off below the barb leaving the pin in place in the bore with removal prevented by the side barb. An unnecessary stub of the tool is left on the pin beyond the barb. There is no teaching in that reference whether or how the pin might be removed and indeed it is apparently not removable because it would be difficult if not impossible to squeeze the barb inwardly and push it on its way back through the bore. The non-removable nature of that pin is also indicated by the fact that the barb is faired on its lower side to slide along the bore during insertion but is sharply cut off on its upper locking side in a manner inconsistent with sliding travel back through the bore.
The hinge pin and installation tool in accordance with the present invention as described herein is distinguishable from the foregoing prior art in that it avoids any retrofit modifications to conventional hinge lugs, and is readily removable whenever desired, and is associated with a break-away manipulable insertion tool making assembly and disassembly quite easy without leaving unwanted stubs on the pin.